1. Field of the Invention
The present invention relates to a method for protecting copyright protection information added to information signals by electronic watermark processing or the like for example, an information signal processing method, an information signal reproducing method, an information signal recording method, and to an information signal processing device, an information signal reproducing device, and an information signal recording device.
2. Description of the Related Art
In recent years, widespread dissemination of digital contents via the Internet, digital video disks, and so forth, has brought about the problem of copyright infringements regarding contents such as pictures and audio, due to unauthorized duplication (copying).
In order to prevent such copyright infringement problems, ways for adding copyright protection information such as copy control information to the contents and preventing unauthorized copying using this added information is being considered.
Such copyright protection information must be added to the information signals in a state of being difficult to alter illegally and difficult to remove from the information signals, in order to effectively prevent unauthorized copying.
Electronic watermark processing is expected to be able to satisfy this requirement. This electronic watermark processing involves a process for embedding information and the like for copyright protection as noise into portions of movie data or music data which are not important to human perception, i.e., portions that are redundant regarding the music or movie data. A specific example of this is spectrum diffusion, wherein information is added and detected using key patterns generated using random numbers, M period sequences, and so forth.
Such information for copyright protection serving as added information embedded in picture data or music data by electronic watermark processing is not readily deleted from the picture data or music data, and altering the copyright protection information is difficult. On the other hand, the embedded added information can be detected from the picture data or music data, even after the picture data or music data has been subjected to filtering processing or data compression processing.
It is expected that effective copyright protection means can be realized by the superimposing processing of copyright protection information onto information signals such as picture signals and the like using the above electronic watermark processing, such as preventing altering so that unauthorized copying can be prevented in a sure manner, copyright protection information can be detected from the electronic watermark so that unauthorized copies can be tracked down, and so forth.
However, with conventional reproducing devices and recording devices, all functions provided to the devices have been usable. Nevertheless, some of the signal processing functions provided to the reproducing devices and recording devices alter the format of the electronic watermark processing with regard to the copyright protection information added to the information signals by electronic watermark processing, resulting in a problem wherein the copyright protection information in the electronic watermark cannot be detected.
For example, in the event that electronic watermark information is superimposed on picture information by performing spectrum dispersion of copyright protection information using random numbers, executing zoom processing on all or part of the image existing in the reproducing device results in interpolation of pixels and horizontal lines, meaning that even using spectrum inverse dispersion will not allow detection of the copyright protection information.
Of course, the copyright protection information in the electronic watermark can be detected if the picture can be restored to the state of the picture signals before the zoom processing was executed, but generally the rate of zooming processing is not known at the time of detecting the copyright protection information, so there is the need to try detecting with several zoom rates by trial-and-error, resulting in massive circuit scales, and extended time spans needed for the detection processing.
In addition to the zoom processing, there are other types of processing which result in changes in the number of pixels or the number of lines, the position of pixels or the position of lines, or interpolation or pruning, such as reduction processing which reduces the size of the image, rotation processing which rotates the image centered on a certain point, inversion processing which inverts the image on a horizontal or vertical axis or on a point, cropping processing which crops away a portion of the image, image shifting processing wherein the displayed position of the image is changed, and so forth. Execution of any of these can result in detection of the added copyright protection information becoming difficult, or, depending on the signal processing, correct detection of copyright protection information may become completely impossible.
In order for detection of copyright protection information to be realized for all such signal processing, a copyright protection method must be developed which deals with these; yet there is also the concern of increasing the scale of detecting circuits thereby.
The present invention has been made in light of the above, and accordingly, it is an object thereof to enable copyright protection in a sure and inexpensive manner, without developing a new copyright protection method.
To this end, according to a first aspect of the present invention, a signal processing method, wherein signal processing is performed on information signals to which copyright protection information has been added, detects the copyright protection information from information signals, and performs control restricting signal processing making detection of the copyright protection information is difficult or impossible, based on the detected copyright protection information.
According to a second aspect of the present invention, an information signal reproducing method reads out information signals to which copyright protection information has been added, detects the copyright protection information from the read information signals, performs control for restricting the processing on the information signals making detection of the copyright protection information difficult or impossible, based on the detected copyright protection information, and subjects the read information signals to predetermined signal processing, based on the control.
According to a third aspect of the present invention, an information signal recording method detects the copyright protection information from the information signals, performs control for restricting the processing on the information signals making detection of the copyright protection information difficult or impossible, based on the detected copyright protection information, subjects information signals to which the copyright protection information has been added to predetermined signal processing, based on the control, and records information signals subjected to the signal processing.
According to a fourth aspect of the present invention, an information signal output method detects the copyright protection information from the information signals, performs control for restricting the processing on the information signals wherein detection of the copyright protection information is difficult or impossible, based on the detected copyright protection information, subjects information signals to which the copyright protection information has been added to predetermined signal processing, based on the control, and outputs information signals subjected to the signal processing.
According to a fifth aspect of the present invention, a signal processing device for subjecting information signals to which copyright protection information has been added to signal processing, comprises: detecting means for detecting the copyright protection information from information signals; and control means for performing control restricting image processing making detection of the copyright protection information difficult or impossible, based on the detection output of the detecting means.
According to a sixth aspect of the present invention, an information signal reproducing device comprises: reading means for reading out information signals to which copyright protection information has been added; signal processing means for subjecting the information signals read out by the reading means to predetermined signals processing; detecting means for detecting the copyright protection information from the information signals read out by the reading means; and controlling means for performing control for restricting the signal processing means in performing the processing on the information signals wherein detection of the copyright protection information by the detecting means is difficult or impossible, based on the copyright protection information that has been detected with the detecting means.
According to a seventh aspect of the present invention, an information signal recording device comprises: recording means for recording information signals to which copyright protection information has been added; signal processing means for subjecting information signals to which copyright protection information has been added to predetermined signal processing, prior to the recording process by the recording means; detecting means for detecting copyright protection information from the information signals; and controlling means for performing control for restricting the signal processing means in performing the processing on the information signals making detection of the copyright protection information by the detecting means difficult or impossible, based on the copyright protection information that has been detected with the detecting means.
According to an eighth aspect of the present invention, an information signal recording device comprises: output means for outputting information signals to which copyright protection information has been added; signal processing means for subjecting information signals to which copyright protection information has been added to predetermined signal processing, prior to the output by the output means; detecting means for detecting copyright protection information from the information signals; and controlling means for performing control for restricting the signal processing means in performing the processing on the information signals wherein detection of the copyright protection information by the detecting means is difficult or impossible, based on the copyright protection information that has been detected with the detecting means.